Draft stabilizer



July 26, 1932. Q D E 11,868,486

DRAFT STABILIZER Filed Nov. 23, 1929 YINVENTOR.

gnk M JW W ATTOPYFV Patented July 26, 1932 UNITED STATES PATENT OFFICELYNN G. IBEADLE, OF DETROIT, MICHIGAN, ASSIGNOR, BY MESNE ASSIGNMENTS,TO TIMKEN SILENT AUTOMATIC COMPANY, OF DETROIT, MICHIGAN, A CORPORATIONOF MICHIGAN DRAFT STABILIZER Application filed November 23, 1.929.Serial No. 409,378.

The present invention relates to draft stabilizers or automatic draftregulating devices for furnaces or other heaters.

As has been set out in the application of Otto Thiel, Serial No.372,895, filed J une 22, 1929, covering a draft stabilizer of which thepresent invention is a development, the draft through a furnace iscaused by the difierence suming that the air in thefurnace flues andchimney is of the same temperature as that without, there will, ofcourse, be an equilibri um. When, however, a fire is started in thefurnace and the gases in the flue and chimney become heated, the draftinto the furnace from the outside is automatically produced. Thestrength'or force of said draft will, of course, depend to a greatextent upon the difference in temperature of the gases inside thechimney and flue and those outside.

Other conditions also influence the force of the draft and among theseconditions is the height of chimney and the condition surrounding itsupper end.

In the ordinary installations of heating systems, therefore, the forceof the chimney drafts will vary between rather wide limits and unlessthe furnaces are given constant attention, the draft will seldom besuited to the greatest efliciency 'of the installation.

In the economical operation of liquid fuel burning apparatus infurnaces, a constant draft through the'furnace is very desirable,

but heretofore has been difficult if not impossible of attainment.

Whilethe previous device as set forth in the application referred to hasbeen found quite satisfactory in many instances, it has been found alsothat as the draft increases above the device, the damper member finallyassumes a balanced position, or condition of equilibrium, in which theforce of the gases on the underside are balanced by the force of thegases entering the opening so that a further increase in draft above thedevice is acpgmpanied by a corresponding increase bew. Among the objectsof the present invention is to move this equilibrium point well outsideof the range of draft likely to occur and thereby render the linerepresenting the draft curve as plotted more nearly straight andhorizontal under all practical conditions.

Other objects will readily occur to those skilled in the art uponreference to the following description and the accompanying drawing inwhich Fig. 1 is a view in elevation of the device. Fig. 2 is a sectionon line 22 of Fig. 1. Fig. 3 is a section on line 3-3 of Fig. 1. In thedrawing, a metal flue pipe is shown at 10 and this maybe the pipeleading from the furnace to the chimney; The present device ispreferably constructed to include a pipe segment 11 adapted to be setinto the pipe 10 and riveted or bolted in place therein.

The pipe segment 11 is provided with a suitable opening 22 and the plate21 is located within the pipe segment 11, being slightly larger in areathan the opening 22 and adapted to completely close the opening when inclosed position, forming what in its conventional form is known as acheck damper or draft check.

The plate 21 is secured to a member 20 which is bent upwardly from theplate and then downwardly again to provide means by which the plate mayclear the edge of the opening 22 when moving about its hinge. The hingefor the plate is formed by the U- shaped end of an arm 26 to which themember 20 is secured at the base of the U. The side portions of the Uare provided withsuitable' is provided with a counter weight 27 whichtirely closed. The outer end of the arm 26 tiallyjadjusted position ofplate 21 can be 77 panied by an increase below.

accurately made. It is preferred to make the counterweight 27 of aplurality of stampings fixed together in order that different sizes ofdampers may be counter-weightedby the use of more or less of thestampings.

In addition to the parts just described, the

plate 21 has mounted near its free end a plate 30 having its outer edgecurved so that when the damper plate 21 has moved into the flue, farenough for the edge 33 of the plate to be near the edge of the opening22, the curved edge-33 of the plate 30- corresponds quite closely to theadjacent curved edge of the opening. This. plate, 30 may be secured toplate 21 as by riveting the end 32 to the plate 21 and may be providedwith suitable brace members 31 to provide rigidity.

The particular shape of plate 30 depends upon the draft curve desired tobe produced and it is not to be understood that a triangular form willnecessarily be used. Other shapes than triangular will produce othercurves.

The device is intended to be placed preferably in the flue extendingfrom the furnace to the chimney and arranged so that the draft is in thedirection indicated in Fig. 2 by the arrow, that is, in the directionadapted to close the openin 22 by the gases acting on the under side 0the plate.

The operation of the device is as set out in the prior application,namely as the chimney draft increases and thereby tends to increase thepull on thefurnace, the tendency of the outside air to enter the opening22 forces the plate 21 inwardly and thereby increases the flow throu hthe opening as well as obstructs the flow rom the furnace past theopening.

As indicated above, without the plate 30 the plate 21 will assume abalanced position in which the. force on the two sides of the plate issubstantially equal and any further increase of draft above the plate isaccom- The plate 30, however, being interposed in the passage throughwhich the outside air enters the pipes tends to cause the entering airto thrust the plate 21 further into the pipe, and as more and more ofthe plate 30 enters the opening 22, its influence .on the plate 21 willbe changed because of its changmg area. By

" plate 30 and plotting the draft .curve, the

latter can be made substantially a straight and horizontal line,over'the entire range of draft likely to occur in the flue 10.

It will be'noted that the plate 30 does not suitably proportioning the-fl ing but only offers a resistance to the enter lng air reaction towhich merely serves to force the damper plate 21 further into the streamof flue gases. The latter are at the same time resisting this inthrustof plate 21, so that at no time can either the flue or draft opening becompletely stopped or the mechanism get into such position as not to beaffected by draft variation. The progressive increase in the effectivearea of plate 30 adds to the force of its inthrust as the draftincreases in the chimney and therefore more effectively blocks the fluegases under conditions of abnormally increased draft.

1 It is, of course, to be noted that, if a curve, other than the onementioned is desired, modification of the contour of plate 30 may bemade so as to produce such curve.

In general terms the regulator is designed for use in any duct carryinggases under variable or constant pressure less than atmospheric Where itisdesired to obtain a regulation of the pressure in advance of thedevice. The motivating force of the regulator is the difference betweenatmospheric pressure and the pressure in the duct beyond the regulator,and the range of possible regulation lies between these two limits.

Now, having described the invention and the preferred form ofembodiment'thereof, t is to understood that the said invention 1s to belimited, not'to the specific details herein set forth, but only by thescope of the claims which-follow.

I claim:

1. An automatic check draft damper for furnaces or other heaters havinga flue for combustlon gases which flue is provided with an opening inits wall, a plate pivoted to said wall at that end of. said openingnearest the furnace and lying withinsaid flue and adapted to open andclose said opening, a second plate mounted in upright position near thefree end of said first plate on the outer surface thereof, said secondplate increasing in width away from said first plate.

2. In combination with a flue having an opening in its wall, a to coversaid opening, said damper being plvotally mounted on said flue wall atthat side of the opening toward the flue inlet and adapted'to moveinwardly of the flue to perm1t 8.11 to enter said opening and a platemountedon the outer surface of said damper and projecting outwardlytherefrom so as check damper adapted to offer resistance to the inflowof air into said opening, whereby reactionary forces tend to thrust saiddamper further into said 3. combination with "a flue having an opening1n its wall, a check damper adapted to cover said opening, said damperbeing plvotally mounted on said flue wall at that side of the openingtoward the flue inlet and adapted to move inwardly of the flue to permitair to enter said opening and a plate mounted on the outer surface ofsaid damper and projecting outwardly therefrom so as to offer resistanceto the inflow of air into said opening, whereby reactionary forces tendto thrust said damper further into said flue, there beingcounterbalancing means for said damper.

4. An automatic draft check damper for i a furnace or other-heaterhaving a flue for combustion gases which flue is provided with anopening in its Wall, a plate pivoted to said wall and within said flueand adapted to open and close said opening and moving in a directioncounter to the flow of combustion gases, a second plate near the freeend of the said first plate on the outer surface thereof and extendingoutwardly from said surface in position to oppose entrance of air intothe opening when uncovered by said pivoted plate, and thru reactionaryforces tend to further increase the opening movements of said pivotedplate.

LYNN G. BEADLE.

